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Faust: Into the Dragon's Mouth

Researchers have catalogued more than 50 kinds of bacteria, including E. coli and a long string of Staphylococcus strains, in the mouths and saliva of wild and zoo-raised Komodo dragons.

So while they weren’t dying to find out, Shedd’s veterinarians were pretty interested in what microbes might be living in Faust’s impressive maw.
Not many, it turns out. A swab taken of his mouth and cultured in Shedd’s in-house microbiology lab turned up Pseudomonas aeruginosa and Citrobacter koseri, two of the usual suspects found in Komodos both in the wild and in zoological collections.

The Pseudomonas species has other favorite habitats, causing one in 10 hospital-acquired infections, a skin condition known as “hot-tub rash” and serious lung, burn and blood infections in people with compromised immune systems. The rod-shaped bacterium, which shows up in tap water, can also colonize your mouth, but it’s unlikely to cause trouble if you’re healthy.

Citrobacter is ubiquitous in soil, water and wastewater, and it’s among the normal “flora” in the human gut. But introduced elsewhere in the human body, it can cause dangerous infections in immunocompromised people and a rare form of meningitis in babies.

So how does a nice zoo-born Komodo dragon like Faust pick up these common but by no means benign bacteria?

“There are microbes everywhere,” says Dr. Bill Van Bonn, senior director for animal health. “You will find things in your mouth and on your skin that, if conditions are right, can kill you. We’re all walking zoos.” (More on that later.)

Komodo dragons enter the world with sweet, clean, sterile mouths, he notes. “The hatchling has to develop his own normal flora. That’s why it’s important that the [zoo or aquarium] environment not be unnaturally sterile. We want the youngster to get colonized by the good bacteria. That’s true for almost every animal that’s born or hatched.”

The “good” bacteria include those organisms that we and other creatures can’t survive without, such as the bacteria that keep our digestive systems functioning. The criterion for “bad” bacteria is rather subjective: They make us sick, or worse. But neither Van Bonn nor Shedd microbiologist Gita Harris is judgmental about the microcritters colonizing Faust’s mouth. “They just happen to be there,” says Harris, and after all, Faust is immune to them.

But where did he pick them up? Van Bonn explains, “Faust roots around in his habitat and jumps in the water, and all that has naturally occurring bacteria that set up shop on and in him because he offers good conditions.”

Faust’s diet of commercially raised, fresh-frozen and hygienically defrosted rats and rabbits does not host the same slew of pathogens found on his wild cousins’ food, including carrion that’s been stewing in the tropical sun for a few days. But his “purpose-bred” provender was alive once, so it isn’t sterile.

“You would expect to find different bacteria [between wild prey and commercial food items],” Van Bonn says, “but it’s not that one’s good or bad, or one’s more dangerous or less dangerous, it’s just different.”

And remember that the deadly drool of Komodos serves a purpose. Speaking about one of the most numerous bacteria identified in wild Komodos, Harris says, “The predominant isolate of Pasteurella multocida is the organism researchers claim kills the prey. Komodo dragons are basically carrion eaters, and if there is no carrion available, they will make some.

“Their mouth flora is adapted to cause the most damage to whatever they happen to bite. Then they just follow the animal until it dies.”

Van Bonn adds, “The reason Komodos have such a reputation is that the bite is pretty violent, and they’re taking down large prey. It’s aggressive, and it’s in a dirty, hot area. Bits and pieces of things will be introduced into the wound, including a lot of the lizard’s teeth, which just come off. So now you’ve got foreign bodies in a wound with lots of bacteria. You’re setting up a perfect condition for an infection that’s going to spread throughout the body and cause the death of an animal.

“It’s one of those situations where Mother Nature could hardly be described as beautiful.”

Van Bonn pauses. “But we haven’t found anything in Faust that is unusual, scary, of high concern, or different from what’s been seen in Fort Worth” among the Komodo group that Faust hails from.

Harris quickly adds, “It doesn’t mean that you want him to bite you.”

So why did aquarists eschew protective hand covering as they held the dragon’s jaws open for the mouth swab?
“He was out,” Van Bonn says. “He was anesthetized, and we didn’t mess around with his mouth until he was completely asleep and the risk of a bite was very small. And obviously we washed our hands afterwards.”

Saliva sample obtained, it was sent to the lab, where Harris put portions of it on different agars, or growth media, to culture whatever types of bacteria might be there. Once something is growing, she can examine it under the microscope and put the sample through biochemical tests to identify it. At the same time, if she’s dealing with a potentially infectious bacterium, she can also test the culture for sensitivity to various antibiotics and pinpoint a treatment even before she knows the name of the organism.

Van Bonn takes pride in Shedd’s microbiology lab, which is comparable to that of a major medical center. In addition, Harris brings 20 years’ experience in clinical microbiology and infectious disease research in human hospitals. “We are one of the few aquariums that have this capability on site,” Van Bonn says.

Harris notes that had there been “big globs of stuff” on the mouth swab, she could have set up cultures for not only aerobic bacteria — those that grow in normal room air — but also for microaerophilic organisms, which require higher levels of carbon dioxide than is present in atmospheric air, and for anaerobic bacteria, which won’t grow in the presence of oxygen. “I would have undoubtedly recovered other organisms,” she says.

Van Bonn adds, “Microbes come and go, depending on local conditions. One swab is just a snapshot of what’s growing at that time and date. If you were to do cultures over a period of time, you’d see all kinds of interesting things.”

But if you think a Komodo dragon is a walking petri dish of death germs, consider this: In a paper published last year in the Proceedings of the National Academy of Sciences, researchers testing skin from the forearms of six healthy people identified more than 180 bacteria species.

“If you were to take any one of those,” says Van Bonn, “and stick it into a nasty wound that’s got a lot of dirt in there, too, it could be tough.”


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